The present invention relates to heat exchangers, and, in particular, to the geometry of fins utilized in conjunction with heat exchanger tubes for air conditioners and heat pumps.
Heat exchangers are used in a variety of refrigeration devices, such as air conditioners and heat pumps, to transfer energy between two mediums, e.g., a refrigerant fluid and ordinary air. The refrigerant fluid is circulated through relatively small diameter tubes, and air is passed over the exterior surfaces of the tubes so that heat may be transferred from the refrigerant fluid, through the material of the heat exchanger tubes, and to the air. To provide a greater amount of surface area for contact with the air to increase the rate of heat transfer, thin metal sheets or fins are attached to the heat exchanger tubes. These fins typically include receiving apertures through which the tubes are insertably installed, and the metal material of the fins is securely held in thermal contact with the outer diametric portion of the tubes. By this thermal contact with the tubes, the fins conduct heat between the externally circulating air and the refrigerant fluid in the heat exchanger tubes. By forced convection produced by a fan system, heat is removed or transferred from the fins to the circulating air. To enhance the transfer of heat energy through the fins between the air and the refrigerant fluid, many fins have surface projections that accentuate the turbulence and mixing of the air passing across the fins. An assortment of different shaped protuberances and louver configuration are known which inhibit the growth of the air or fluid boundary layer formation on the fin surface, and which increase flow turbulence and flow mixing to improve heat transfer characteristics.
One shortcoming with many existing fins is that their designs result in an inefficient usage or wastage of the materials of construction, which in turn undesirably adds cost to the heat exchanger. For example, as disclosed in U.S. Pat. Nos. 5,170,842 and 4,907,646, many fins are generally rectangularly shaped when assembled in heat exchanging relationship around a row of heat exchanger tubes. For this fin shape, an appreciable amount of material used at a location both between adjacent tubes and offset from the row of tubes obtains only a relatively small increase in the heat exchanging capabilities of the fin. Consequently, if this fin material could be arranged at a location where its heat exchanging capabilities could be better exploited, a more efficient fin design would result. Other specialized fin designs, such as disclosed in U.S. Pat. No. 4,771,825, may result in undesirable amounts of scrap material or waste being produced during fin construction.
Another shortcoming of many existing fin configurations is exhibited when the stacked fins and tubes of a coil are bent or curved to conform to the desired shape of a heat exchanger. For example, heat exchangers may need to be formed in a cylindrical shape for use in outdoor air conditioning units. Especially for wider fins adapted for use in multi-row heat exchangers, the stacked fins have a tendency to become crushed together during their bending, thereby partially or possibly totally closing off the spacing between certain adjacent fins. This fin crushing is undesirable for a number of reasons, including that the heat transfer capabilities of the fins are compromised, and further that the overall aesthetics of visible fins is lessened.
Thus, it would be desirable to provide a heat exchanger which overcomes these and other shortcomings of the prior art.